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GNU R package for discrete data models

This package consists of R functions developed at the Political
Science Computational Laboratory at Stanford University; it currently
includes models for count data (hurdle regression and zero-inflated
negative binomial and Poisson models), ordinal probit and logit (also
available in MASS via polr), and an item-response theory model. Also
included are Vuong tests for non-nested hypothesis testing and
convenience functions for handling roll-call vote matrices.